1. Field of the Invention
This invention relates generally to xerography and more particularly, to a method and apparatus for forming a multicolor proof print from at least two light transmitting color separations.
2. Description of the prior art
It is known in multi-color printing to make use of color separations, i.e. partial images in each of the three basic colors (yellow, magenta, cyanogen) usually supplemented with a partial image in black. Different techniques are known for obtaining such color separations from the original to be reproduced. Before commencing the final production printing run of such separations, a check must be made to ensure that a satisfactory final result is obtained with the color separations formed. For this purpose, a proof print normally is made on a proof printing press. This is a time-consuming process. Furthermore, the proof printing press required for such procedure is expensive.
The general state of the art with which the present invention is concerned is described in U.S. Pat. Nos. 3,999,987 and 3,836,244. Additionally, U.S. Pat. No. 4,120,577 describes the problems which occur when making color reproductions as a result of the charge which remains on the electrophotographic material after exposure and supply of toner. Said U.S. Pat. No. 4,120,577 teaches removal of the residual charge by use of a special corona-electrode. In the present invention, such residual charge is removed by an extra exposure step.
The present invention provides a method and apparatus for forming a multi-color print in a quick and inexpensive manner and in which the print corresponds so much with the print formed on a printing press that it is possible to make a very accurate assessment of the color separations.